It's a long trek to Rivet City, and you should avoid unnecessary hostile encounters.

Fast travel to Farragut West Metro Station by using the worldmap. You're in for a very long walk to Rivet City. Walk all the way past the river, avoid the many enemies you come across (unless it's a really fast Super Mutant). Try to discover Tepid Sewers and Duvok's Place (just south from Dupont Station on the worldmap) You'll probably also come across a merchant along the way, and when you finally arrive at Rivet City, another merchant will be available to you. Climb the stairs and look around for an intercom near the sick man in order to enter the ship. State your business, be honest, and get on board.

Once on board, look on your left for two boxes of ammo, they hold [FLAMER FUEL x83] twice, and [.32 CALIBER ROUND x4]. If you look to your right after investigating the ammo boxes you'll find a medbox on the floor that holds a [BLOODPACK], [BOBBY PIN], [RAD-X] and a [STIMPAK]. Now go more to the left and head up the stairs until you reach the roof. Look around for a door that leads to the Bridge Tower. From this room, head left and through the door. Go down two flights of stairs and enter through another door. Here, walk through the tunnel and follow the signs ‘Science Lab' until you get to a door once more.

Look around for Doctor Li and talk to her about everything. You can also talk to an older man called Dr. Zimmer and start the MQ: The Replicated Man. When finished, explore the room and get the [INTELLIGENCE BOBBLEHEAD] from one of the tables. Be sure to stop by the Marketplace before you leave the city, because it's a great place to shop; They have nearly everything, if you have the caps. Sell all the things you no longer need.

Ah, very nice, a permanent boost for your INT.

Jefferson Memorial:Weapon of choice in this area? The hunting rifle is preferred, so you can grab your ammunition back from the Super Mutants. Pop their heads with it, take a lot of shelter, and keep your clip at the full 5 bullets before recklessly diving into a battle. Secondary weapon choice would be the Assault Rifle.

Jefferson Memorial isn't all that far away, and if you've visited it before you can fast travel towards it. Locate the door to the gift shop, and prepare for battle.

The entrance to Jefferson Memorial requires you to circle around the building and deal with the Super Mutants.

Many Super Mutants and Centaurs are roaming around, so grab your best guns and start downing them. The room on the south also has a turret, which most likely gets destroyed by a Super Mutant at some point. You can turn it off by using the terminal. In this room you'll find [3x STIMPAKS] and a [MED-X] in the medbox under the Gift Shop sign. It's possible to use the sinks on the west for healing. In the east room you can check the ammunition boxes to find [5.56MM ROUNDS x18], [10MM ROUNDS x8], and two [.32 CALIBER ROUNDS x5] on or under the shelf below.

Go south and head through the door that leads to the basement. Fight your way through 3 Super Mutants and go east. Collect a useful [STIMPAK] in the room to your left, then head downstairs. Kill another Super Mutant, go through the hall south and kill another. In this hallway you can find two [.32 CALIBER ROUNDS x5], [5.56MM ROUNDS x24] and [RADAWAY] on some shelves. Also check the Ammo Box to find [10MM ROUNDS]. In the room to the west of these shelves, grab all five notes of relevance on the desks, then backtrack slightly and head west. In a room ahead, another Super Mutant lurks. Dispose of him and return to the gift shop area. You can sleep in the basement now, by the way.

Enter the Rotunda and dispose of the two Super Mutants. Don't worry about health, you got a place to sleep nearby anyway. At the end of the stairs (before entering the round room) you can grab another bunch of files to complete your objective. Have a listen to them, especially #10, restore any lost health by sleeping, and leave the area.

These are the files you're looking for. Makes you wonder how dad snuck past all these muties..

Smith Casey's Garage/Vault 112:The place you're headed to is once again, far, far away. Travel to Megaton and go from there. When you start getting close, you'll want to avoid the train tracks at all costs. You don't want limbs flying off due to stepping onto mines and there are tons of Raiders that way. Avoid it and continue to Smith Casey's Garage. Enter and dispose of the few creatures inside. You can grab two [FISSION BATTERIES] and a [NUKA-COLA QUANTUM] in the first room, and [10MMROUNDS x9], [.32 CALIBER ROUNDS x10], [SCOPED .44 MAGNUM] and [.44 ROUNDS] from the gun cabinets in the next room. There is also a medbox hanging near the doorway holding a [BLOODPACK], [DIRTY WATER] and [STIMPAK].

Hop inside the empty cabin; everything to find your dad.

[MED-X], [BLOODPACK x2], [STIMPAK], [MENTATS] can be found in the room the most southwest. Explore all other rooms as well, and hop into the abandoned cabin terminal whenever you're done. You probably can't unlock the door that requires a 75 Science Skill points terminal to open it, so that'll come later.